1. Field of the Invention
This invention relates to motorized and automated pipetting devices, and to electronically controlled apparatus having memory capability for aspirating and/or dispensing a pre-determined quantity or quantities of liquid. This invention is particularly related to a pipette gun type apparatus which is programmable to automatically dispense or aspirate uniform amounts of liquid.
2. Related Inventions
This invention is related to inventions disclosed in U.S. Pat. No. 3,963,061 which issued Jun. 15, 1976; U.S. Pat. No. 4,475,666 which issued Oct. 9, 1984; U.S. Pat. No. 5,090,255 which issued Feb. 25, 1992; U.S. Pat. No. 4,967,606 which issued Nov. 6, 1990; U.S. Pat. No, 4,448,752 which issued May 15, 1984; and U.S. Pat. No. 4,896,270 which issued Jan. 23, 1990.
3. Background and Prior Art
Motorized and/or automatic pipetting devices of the prior art traditionally used and still use standard piston-type pumps to create suction or positive pressure for moving liquids. These types of pumps, while they are generally successful for the objectives set, have a variety of disadvantages. First, of course, are the structural requirements of a piston-cylinder mechanism having close tolerances, good seals, valves, valve seats and mechanisms to operate the valves and transmission assemblies to couple an electric motor to the piston. This kind of design automatically increases cost for manufacture and assembly of numerous precision parts and for wear, maintenance and replacement of parts. The second disadvantage is the difficulty or often impossibility to clean parts which are dirtied or contaminated by the fluids pumped. Where cleaning is even possible, time and expense is a major detraction. A third objection in some high speed operation pumps is the noise and/or vibration.
As indicated earlier, prior art and current automatic pipetors are such a great improvement over manual pipetting that users and manufacturers have widely accepted the basic electric motor piston-cylinder pump as the standard apparatus and focussed development efforts on other aspects of operation, such as electronic controls, better or different motors, valves for the pumps, and materials.
Other types of pumps exist and are used for appropriate functions, but not for hand-held pipetors, apparently for various reasons. A peristaltic type pump, for example, has not been used for hand-held automatic pipetors, first, because the essentially universal piston-cylinder pumps are a known and reliable and assumed entity, and second, because peristaltic pumps are traditionally used either for continuous through-flow or for liquids or both, and then only in stationary apparatus.
Each of the disadvantages of traditional and current automatic pipetors with piston-cylinder pumps discussed above have been resolved by either accepting the problem or by using more complex and expensive valving, motors and associated controls, or in the case of contaminated apparatus by simply discarding same.
The present invention utilizes a new combination of components and provides improvement in all the areas discussed as explained below.